Work machines such as tractors are often used to pull implements such as box blades, compactors, rollers, scrapers, etc. These implements may be supported by wheels or may drag along the ground. Implements are typically not dedicated to a particular work machine and therefore are in the need of a fast, efficient and effective means to couple the implement to the work machine (hereinafter tractor). Tractors typically have a three point hitch arrangement and many implements only use two points of the three point hitch arrangement particularly those implements utilizing one or more wheels for support. Two point hitch arrangements utilize the two draft arms which are selectively moveable between elevated and lowered positions and retainable at one of various positions between a lowered position and an elevated position. A cross bar may be secured to the draft arms to extend therebetween and is typically pivoted to the draft arms for rotation about a generally horizontal axis or an axis generally parallel to the axis of the rear wheel axles of the tractor.
Numerous types of couplers have been devised for connecting an implement to a tractor. The couplers may be divided into three categories. The first category is the coupler that attaches to a draw bar with multiple pivots trailing behind the draw bar a substantial distance. Examples of these can be found in U.S. Pat. Nos. 5,706,901, 5,531,283 and 4,838,015. This style of coupler, unless the implement is supported by front and rear wheels can apply a significant amount of downward force to the tractor hitch and can result, in some cases, in lifting the front wheels of the tractor from the ground. To avoid this, implements have been provided with front and rear wheels when such implements or their loads are heavy.
A second type of coupler releasably attaches the tongue of the implement to the draw bar as for example with a ball or pin or the like. The tongue rests on the draw bar and pivotal movement is accomplished by rotation about the ball in multi-axes or about a hitch pin through holes within the coupler arrangement. While effective, the freedom of movement about a ball or hitch pin is limited. A pintle hook is another such type of hitch.
A third form of coupler arrangement is shown in U.S. Pat. No. 2,091,009. As shown, and described, the coupler is required to be forward of the rear wheels in order to prevent lifting of the front wheels when heavy loads are encountered. To accomplish that goal, a large U-shaped yoke bridges the drive train in front of the rear wheel differential allowing pivoting in a forward and rearward direction by being hinged at pins connected to the drive train. Second and third pivots are provided to provide both steering pivoting and irregular terrain pivoting. However such an arrangement is cumbersome and eliminates, at least for modern tractors, the ability to use the seat on the tractor. Also, because of the large height of the coupler, large moments (torque) will result. Such an arrangement would also be difficult to attach an implement to the tractor and the ability to raise and lower the implement is precluded.
One common element to many of these hitches, particularly of the first and third categories just described, is the ability to provide pivoting about three distinct axes using three separate pivot arrangements. Further, the first and third categories tend to be complex mechanisms that do not accommodate the applied forces necessarily very well. Thus, there is a need for an improved coupler and tractor/implement/coupler arrangement.
The present invention involves the provision of a tractor, implement and coupler arrangement that includes a coupler attachable to the draft arms of a tractor and having three pivot devices for allowing the tractor and implement to pivot relative to one another about three axes. The axes of the pivots are such as to substantially intersect with one another to provide a low profile coupler arrangement. The coupler interconnects the tractor hitch arrangement and hence the tractor to an implement having a draw tongue. The tongue is preferably, at least for certain types of implements, a goose neck type tongue to help provide clearance for tight turns without interfering with the rear wheels or other portions of the tractor. The implement may use support wheels or may have support wheels that are selectively engageable with the ground or in certain cases the implements may not utilize wheels for support. The coupler permits the use of a link from the third point of a three point hitch, in a selective manner, to elevate certain implements for transport by using the three point hitch arrangement on the tractor.